The compound 1-(4-amino-6,7-dimethoxy-2-quinazolinyl)-4-( tetrahydro-2furoyl)piperazine is known by the common name "terazosin." Terazosin is known to have utility for the treatment of hypertension, benign prostatic hyperplasia, and congestive heart failure. The compound and methods for its preparation are disclosed in U.S. Pat. No. 4,026,894. This patent discloses, in Example VI, a method of preparing terazosin which produces a non-solvated crystalline polymorph of the compound which, for the sake of identification, is termed crystalline "Form I" of the compound throughout this specification and the appended claims.
Pharmaceutical compositions comprising terazosin or a pharmaceutically acceptable salt are claimed in U.S. Pat. No. 4,112,097 together with their therapeutic use for the treatment of hypertension.
The dihydrate crystalline form of the hydrochloride salt of terazosin is marketed under the trade name Hytrin.RTM. and is the subject of U.S. Pat. No. 4,251,532.
The R(+)-enantiomer of terazosin is disclosed and claimed in U.S. Pat. No. 5,212,176, together with pharmaceutical compositions comprising the R(+)-enantiomer, and methods for the use of the compounds and its compositions for the treatment of hypertension, hyperinsulinemia, congestive heart failure, and benign prostatic hyperplasia.
U.S. Pat. No. 5,294,615 discloses a non-solvated crystalline polymorph of terazosin hydrochloride which is distinct from Form I referred to above and, for the sake of identification, is designated in that patent and in this specification and the appended claims as crystalline "Form II.